Abstract: 【Objective】Mechanical grain harvest is the developing direction of maize production, and harvest quality is the main factor affecting its popularization and application. This harvest way in China is still in the preliminary stage. The application areas are larger in the Northwest and Northeast China while experimental demonstration is just actively carried out in Huang- Huai-Hai summer corn area. In this study, the influence factors on harvesting quality of mechanical grain harvest in summer maize were analyzed to provide supports for popularization and application of the technology. 【Method】From 2013 to 2015, twenty three different maize cultivars were planted in Xinxiang, Henan. Twice harvests were conducted in 2013 and 2015 and once in 2014. The moisture content and yield were measured before harvest. When mechanical harvest was finished, kernel samples were taken out from the harvester to investigate the moisture content immediately. Then, the grain broken rate and the impurity rate were measured in laboratory by hand-picked method. The ear and kernel loss rates were investigated in the field sample areas after harvest. 【Result】From 2013 to 2015, the results from 131 samples showed that corn kernel moisture content ranged from 20.80% to 41.08% and grain broken rate was between 4.98% and 41.36%. Grain broken rate increased with the rising grain moisture content. There were 38 samples that broken rate was below 8%, accounting for 29.01%. When kernel moisture content was under 26.92%, the broken rate could confirm to the standard of 8%. The results from 134 samples showed that the impurity rate was between 0.37% and 5.28%. There were 107 samples with impurity rate below 3% which accounted for 79.85%. The impurity rate also increased with the rising grain moisture content. From 2013 to 2014, the impurity rate did not meet the standard of 3% until grain moisture content was below 28.27% while the impurity rate was all below 3% with grain high moisture content in 2015. The loss rate from 108 samples ranged from 0.18% to 2.85% all of which confirmed to the national standard. Therefore, the loss rate didn’t limit the mechanical harvest quality. In this experiment, when kernel moisture content was lower than 26.92%, the broken rate and the impurity rate were below 8% and 3%, respectively, and the loss rate met the national standard simultaneously, which could ensure the quality of mechanical grain harvest. The study also found that there were significant differences in the broken rate and the impurity rate among different cultivars, representing the importance of proper cultivar. 【Conclusion】 Corn moisture content is the key factor for the quality of the grain mechanical harvest. Significant differences existed in harvest quality among cultivars when grain moisture contents were similar. Because of different growing conditions such as temperature between years, the grain moisture contents at harvest were different, but it is feasible for Huang-Huai-Hai summer maize region represented by Xinxiang, Henan to ensure the quality of grain mechanical harvest by choosing the adapted cultivars and adopting appropriate sowing and harvesting time.

Key words: maize, grain mechanical harvest, harvest quality, grain moisture content